Holding definitely isn't completely incapable and his ability on the ball is underrated because of his ungainly technique I think. None of this detracts from the fact Saliba is a big loss but it's not like we're airlifting Gavin Hoyte into defence.
In my mind, it does however make us more reliant on Partey as Holding + Jorginho feels a little immobile. So there are broader concerns in terms of our squad depth here.